| Budget Amount *help |
¥2,000,000 (Direct Cost: ¥2,000,000)
Fiscal Year 1994: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1993: ¥1,200,000 (Direct Cost: ¥1,200,000)
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| Research Abstract |
The abalone Sulculus diversicolor contains abundant myoglobin in buccal mass. The myoglobin consists of 377 amino acid residues and the molecular mass is 41,000Da, which is 2.5 times larger than that of usual myoglobin.Sulculus myoglobin can bind oxygen reversibly, and thus functions as an oxygen carrier. The cDNA-derived amino acid sequence showed no significant homology with those of any other invertebrate myoglobins and hemoglobins, but surprisingly showed 35% homology with a vertebrate tryptophan degrading enzyme, indoleamine dioxygenase (IDO). The gene structure consisting of 14 exons and 13 introns (15.3 kbp) of sulculus myoglobin has been determined. Compared with the gene of human IDO (10 exon-9 intron structure) , the splice junctions of 7 introns were exactly conserved between the two genes, suggesting that these introns have been conserved for at least 600 million years. Sulculus gene has additional 5 introns, one of which is located outside the coding region. The interferon-stimulable response element-like sequence, which is present in many different interferon-stimulated gene promoters, is present in the 5'flanking sequence of Sulculus gene, as in human IDO gene. From these results we conclude that Sulculus myoglobin evolved from a IDO gene. The birth of Sulculus myoglobin must be a typical case of functional convergence. The IDO-like myoglobin is unexpectedly widely distrbuted among gastropodic molluses, such as Sulculus, Nordotis, Battilus and Chlorostoma.
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